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In close collaboration with Veidekke, architect LPO and other consultants, we have worked on this unique office building," says Head of the Building Technology Section at Dr.techn. Olav Olsen, Eivind Sinding-Larsen. The main element of this building is a greenhouse gas emissions reduction of 65 per cent compared to an objectively defined reference building. Concrete is one of the largest contributors to greenhouse gas emissions, and this is a concrete shell building, so we worked a lot to achieve large emission cuts on the concrete.

In the pilot project, four different concepts were developed for the main load-bearing system. Concepts for slack-reinforced concrete, solid wood, precast concrete and post-tensioned concrete were established with realistic dimensions. Greenhouse gas calculations were then carried out for all four alternatives. Based on greenhouse gas calculations, among other things, they ended up going for a support system with slabs in post-tensioned concrete. The tension cables enable extremely slim slabs that significantly reduce the concrete volume. In addition, there are few pillars and pile points. The building is 18.2m wide, but has only two rows of columns and a slab thickness of only 250mm.
In the concrete used, 100% of the coarse aggregate consists of recycled concrete from demolition masses. It was decided early in the project to try to use this type of aggregate, and a great deal of work was done to test and document the properties of the concrete recipe before the detailed design began.

The concrete also consists of a special type of binder, CEMIIIb, where 40% of the cement is replaced with slag. This results in a concrete with a very low greenhouse gas footprint. The effect of the low cement content means that the curing time is increased and heat generation is limited. When casting at low temperatures, measures had to be taken with preheating and covering to ensure the desired strength development.

Read more about the project at bygg.no (norwegian only)